Automatic control for headlights of motor vehicles



Oct. 21, 1952 PARDUE ET AL 2,615,079

AUTOMATIC CONTROL FOR HEADLIGHTS OF MOTOR VEHICLES Filed Jan. 5, 1951 2 SHEETS-SET 1 Ill 22/ 55 66 67 68 3 Pal A Oran. Hi yin; J

7 70 6 [/bcrfll ara Ht 62 BB I 59 7Z (Ittorneg 1952 E. M. PARDUE ET AL 2,515,079

AUTOMATIC CONTROL FOR HEADLIGHTS OF MOTOR VEHICLES Filed Jan. 5, 1951 2 SHEETS-SHEET 2 M3 L[ L u} INVENTORS RALPH HIGGINS ELBERT M. FARDUE THEIR ATTORNEYS Patented Oct. 21, 1952 AUTOMATIC CONTROL FOR HEADLIGHTS OF MOTOR VEHICLES Elbert Matthew Pardue, Wilkesboro, N. C., and Ralph Oren Higgins, Chase City, Va.

Application January 3, 1951; Serial No. 204,224

(Cl. 175 a21) 4 Claims. 1

The present invention has to do with the headlights of a motor vehicle and is concerned primarily with the provision of a control which Will automatically deflect the beam coming from the headlights upon the approach of an oncoming vehicle and then restore the beam to its elevated condition after that vehicle has passed.

At the present time the conventional automobile includes headlights which are designed to throw either a high beam or a low beam. While the high beam is the more desirable from the viewpoint of the driver of the car, it constitutes a menace to the driver in an approaching vehicle. Hence, just about every modern automobile is provided with a foot switch which may be operated'by the driver to deflect the headlight beam or raise it as occasion demands.

Such an arrangement has not proven to be entirely satisfactory because in many instances the driver will not bother to operate the switch;

his attention may be directed to other matters;

he may not be aware of the fact that the beam is elevated; or he simply disregards the rights of the oncoming driver.

This highly unsatisfactory condition has long been recognized by automotive engineers working on this problem and various attempts have been made to provide a control for the headlights which is automatic and which will respond to the lights of an approaching vehicle to deflect the beam and raise it after such vehicle has passed.- The problem has been recognized and many have attempted to solve it. Certain controls have been provided as a result of these efiorts, but the fact remains that as yet such controls have not come into any appreciable use.

The failure of the car manufacturers and the public to adopt the now available automatic headlight controls is believed to be directly attributable to certain shortcomings in the controls themselves. Such controls must consist essentially of electronic circuits including a photo-electric cell. These circuits are operated from the battery of the car. As the car is continued in service, the battery runs down and the circuits must be adjusted to compensate for this variable condition. One of the main objections to the now known controls of this type is the necessity of adjusting it from time to time.

From the very natureof the control device, it is responsive to light. This light should be onlyt-hat coming from an approaching vehicle. However, there are, under practical conditions, road signs and other sources of light, either direct or reflected, which affect the controlat the wrong time. An important defect in the now known automatic headlight controls is the failure to effectively screen off or eliminate such extraneous sources of light, leaving the control responsive only to the light coming from an approaching vehicle.

With the foregoing conditions in mind, the present invention has in view as its foremost objective the provision of an automatic headlight control of the character indicated, which is self-compensating for variations in the operating conditions of the car in which it is installed. Thus, once the control is installed in an automobile, it is unnecessary for the owner to make adjustments from time to time. The device itself compensates for such variations as changes in the battery and the like.

More in detail the invention has as anobject v the provision of an automatic headlight control of the character indicated which includes means for adjusting thecontrol of the voltage of a particular car battery. Once this adjustment is made, such as at the time of installation, there is no need for any further adjustment on the part of the car owner.

Another highly important object of the invention is to provide, in an automatic headlight control of the type aforesaid, means for eliminating or rendering non-effective all lightexcept that coming from the headlights of an approaching vehicle. This end is accomplished'by two factors. In the first instance, the photocell unit, which is really an electron-multiplier phototube, is housed in a casing which is positioned beneath the left front headlight of the car. This casing is light tight except for an aperture at the front, and the tube is so positioned in the casing with respect to the aperture as to permit only light coming from within a certain angle to reach the tube.

In the second instance, the circuit includes certain instrumentalities which,

apparent and in part be hereinafter stated as the description of the invention proceeds.

The invention therefore comprises an automatic headlight control for a motor vehicle which includes an electronic circuit that is self-compensating for voltage variations, together with a casing which houses the phototube and which casing is constructed and designed to properly limit the light which reaches the phototube.

For a full and more complete understanding of the invention, reference may be had to the following description and accompanying drawings wherein:

Figure 1 is a wiring diagram of the automatic headlight control of this invention;

Figure 2 is a view in front elevation of a motor car, illustrating the position of the casing housing the phototube;

Figure 3 is a top plan view of the casing taken on an enlarged scale with certain parts shown with broken lines;

Figure 4 is a fragmentary view of the left front fender of the car with a modified form of casing applied thereto; and

Figure 5 is a top plan view of the modified form of easing.

General environment From the very nature of the invention the automatic headlight control is intended to be installed in the present day conventional automobile. Such an automobile ordinarily includes a battery which constitutes a source of direct current. The automobile also includes a frame to which any circuit or electrical element may be grounded. Headlights are included and an electrical circuit therefor. Included in the circuit is a low beam light -y and a high beam light relay. These relays are ordinarily controlled by a manually operable switch including high and low beam contacts. This switch is commonly referred to as the dimmer switch. The automobile also includes the usual front fenders in which the headlights are mounted.

All of the structure and mechanism so far described is present in every conventional automobile. Hence, it is deemed unnecessary to illustrate such matter in the drawings any more than is necessary to bring in the relation with the elements of this invention.

An automobile is depicted in Figure 2 and referred to in its entirety by the reference character A. It includes a right front fender l0 and a left front fender I! which carry headlights [2. The automatic control of this invention is embraced in two units which are connected by a multi-wire cable. One of these units takes the form of a casing which houses the phototube and which casing is mounted in the left front fender ll immediately beneath the headlight I 2. The other unit is installed in the car in a convenient location and is preferably sealed tight after installation. The latter unit houses the various electrical and electronic devices making up the control.

As illustrated in Figure 2, a casing B is installed in the fender ll beneath the headlight 12. The construction of this casing is shown in greater detail in Figure 3. A modified form of casing is shown as installed in the automobile in Figure 4 and is designated C. The casing C is illustrated in detail in Figure 5.

The phototube casing The simplest form of phototube casing is shown in Figures 2 and 3. As illustrated, the casing B is of a flat, rectangular formation and is completely enclosed except for an aperture l3 formed in the front or exposed wall. This aperture [3 is of rectangular formation, being about three times as long as it is high. Thus, by way of example, the aperture [3 ma be one-half inch high and one and one-half inches long. These dimensions are not critical, although an essential requirement is that the aperture be longer than its height.

A phototube P is mounted in the rear of the casing 13 remote from the aperture IS. The spacing between the aperture 13 and the phototube P is of importance because this spacing determines the angle through which light will pass through the aperture and strike the phototube. Obviously the greater the spacing, the narrower the angle and vice versa. Purely by way of example it may be noted that with the opening l3 one and onehalf inches by one inch, the phototube P is spaced six inches therefrom.

The casing B is installed in the car with the opening 13 having its longest dimension in a horizontal position. This provides a comparatively wide horizontal angle, but a narrow vertical angle. The object of this arrangement is to provide for only light from the headlights of an approaching vehicle passing through the opening onto the tube. The casing B is, of course, light tight and the only light which may enter thereinto is through the opening IS.

A more sensitive arrangement for mounting the photocell is illustrated in Figures 4 and 5. In this form the casing C has a front wall [4, an outer side wall I5, an inner side wall I 6 and a rear end wall IT. The outer side wall [5 is somewhat shorter than the inner side wall l6 and the front wall 14 is provided with a circular opening in which is mounted a lens 18. This lens is positioned at an angle with respect to the sides of the casing which affords an outer facing of the lens I8. Extending between the rear wall I 1 and the side wall [6 is a partition [9 which carries a phototube P which, it will be noted, is disposed at an angle with respect to the side wall. Mounted against the inner side wall I6 is a narrow strip reflector 20. The forward end of this strip is positioned at the front wall [4 substantially at the lens opening, while the rear end is at the phototube P.

The lens l8 has a focal length somewhat less than the space between the lens and the phototube P. When an oncoming car first comes into range, the light from its headlights passes through the lens l8 and is conveyed directly onto the phototube P. As the two cars come closer together, the light passing through the lens l8 will first strike the reflector 20 and be reflected by the latter onto the phototube, and this condition remains right up to the point where the two cars pass. Thus, there is always sufiicient light coming from the headlights that is directed onto the phototube to hold the headlight beams deflected until the two cars pass, as will be later pointed out.

This lens and mirror arrangement is important from two aspects. When the light from the approaching headlights is farthest away, the entire area of the lens gathers the light and puts all the light so gathered onto the phototube. This means that the control is most sensitive when the lights are almost directly ahead. This sensitivity is suihcient to cause the control to operate and defiect the headlight beam being controlled. However, once this operation is accomplished there is no ineed. forsensitivity to'the same degree to hold the. headlight beam deflected. As the two v cars comeicloser together there isenou'gh lightgathered by the lens and reflected by the mirror onto the :phototube to prevent any change in the control. Thislpermits the use of a relatively narrowireflecting strip which, of'course, reduces the vertical' angle from which light can reach the cell. This prevents lights from signs or other sources on the side of the road from 'aifectin the control Jtotthe :extent which they otherwise would. This modified form of thehousing is highly directional and results ina positive operation of the control.

T he control circuit Referring now more particularly to Figure l, thecircuit of the control will be described. A line 21 has one end connected to the high beam contact of the manually oper-ably high-low'switch on the car suchxconnection being represented at 22. Through the'connection 22 the line 21 is connected to the battery of the car.

The line 21 extends toa vibrator shown at 23. This vibrator serves to convert the direct current coming from the battery into alternating current.

A transformer is referred to in its entirety by the reiference character T. It includes -a primary 24, the oppositeen'ds of which are-connected by lines 25 and-26 -to the vibrator 23. Another line 2] has one end'connected to the primary substantiallymidway thereof while its other end is connected to: a variable resistor 28. From the variable resistor-28 a line 29 extends, and this line is grounded to the framework of the caras indicated at 30. Included in the line .29 is a manually operable switch-3l which preferably is a single pole, single 'throw' switch of any type. The switch 3| is located ina position where it is accessible to the driver. When this switch 3| is opened the control circuit-is disabled; when it is closed the control circuit is rendered effective. Thus, the driver may throw in or cutout the control as he wishes.

Included asap'art of the-powertransformer T r is aseconda'ry'32. One end ofthe secondary-32 'is grounded by a line 33 as indicated at 34'. From the other end of the secondary32 a line-35 is taken. "This line 35' goes to thepho'totiibe P, as will be later described. A bufier condenser 36 is connected in parallel-across the secondary 32 by a line '31 which extends on one side to the line 35, and another line 38 on the other side which extends to the line 33. The buffer condenser 35 serves to prevent voltage surges that might possibly damage the vibrator 23.

The -power transformer'T also includes another secondary 39 which operates the relay'R and the thyratron tubeto be later described.

'In' the power transformer T the primary 24 has fourvolts impressed thereacross. This creates a voltage of i 1100 volts of alternati-ng'current in the secondary 32,'and which voltage is used to excite thephototube P. A voltage of 110 volts is excited in the secondary 39 which is effectiveon therelay and thyratron control tube.

.A relay indicated at Zlt is'a-p'late-circuit relay of the single pole. doub'le throw type. It includes .a coil 40 and plates ll. One endof the secondary-39is connected to one end of theirelay coil 40 bya line 42. Another buffer condenser 43 is connected in parallel across the secondary 39 by lines 44 and45. The line has one end connected to the point of junction between lines 33 and 38, and one end of the secondary -is-connected to the line 44 betweenthis junction. and the condenser 43 as indicatedat 19'. The line 45 extends from the other side of the :condenser 43 to line 42.

Axthyratron controlrtuberis shown at V.. Itincludes-ananode 46 which is connected ;by .a line 41 to oneend of the coil4fl. A. relay by-pass-condenser is shown at 4.8.' "It is connected inzparallel across the coil .40 by lines 43 and 50;. Thiscondenser..48 serves two purposes; It preventschatter ofitherelayicontacts and makes .the relay slow opening. A line 51 has one end .connectedrto the line between :the' condenser and the line 42 and its'other end to afixediresistor 52: The resistor-52 is a current limiting'resistor which determines the voltage drop :across the variable resistor 53 which is conn'ected in series with the resistor 52 by a line .54. One endof the variable resistor isgroundedas shown at 55'. This resistor 53 determines the voltage at which the thyratron tube V will fire. That is, the resistor 53 isradjusted to determine the amount o'f light Whichris'required by the .phototube P before the control unit will operate. Once'the resistor 53 has been adjusted no furtheradjustment is ordinarilymade. Thatlis, the adjustment is not an operating adjustment.

The thyratron tube V includes a cathode 56 WhlChjlS connected-by a line 51 with the variable resistor 5.3. .A line- 58 extends-from the grid of the'thyratrontube Vito the grounded-connection indicated at-59. Included in thislineare'two fixedresistorsatlfl and 6 I, and a condenser 62. Between the .resistors 60 and =61 a line 63 iscon- .nected'tothe line. 58, and this line is grounded as indicated at 64. Included in this line 63'isa condenser 65.

Connected to the line-58 between the resistor -3l and the condenser'62 is a linefiii'which goes to the phototube P. Included in this line 65 is a resistor 61, and between theresistor 'fil and the phototube P there is a line 68 which is grounded as indicated at 59,. and which includes a condenser TEI. The "condensers 65, 162, and T0, 'together with the'resistors 6! Sand '61, function as a low pass filter which prevents a fluctuating light from affecting the thyratron tube. Due to the fact that only currents below a certain critical frequency can pass this low pass filter,- only light of practically steady intensityv can cause the thyratron tuberto fire. The practical eifect of this is that. reflected lights from onor near the road .are prevented'toa great extent from operating the control to. lower the. headlight beams.

The purposeof the'resistor'fifl is to prevent sudden -discharge 'of the condenser 65 through the thyratron tube V wheneverthe latter fires. .Such

sudden discharge could exceed the capacity of the thyratron tube and damage it. It could also lower the-charge on'the .cjondenser'65 to such a point thatithe discharge in thefthyratron tube V' would not have timeito transfer from the starter anode to .the plate before the voltage on the condenser 65 droppedqso low'lthat the. tube could nolonger fire. it the discharge. cannot transfer ffrom the starter anode to 'theiplate, no plate current :would flow and therelay would not operate.

The line r66 is shielded as indicated at "H, and the shieldis grounded'as shownat 12.

The relay R includes a switch represented at 13. This switch is connected by .a line l4 to the line 2 I. The switch is a double throw, and in one position isadapted ito'be connected to a'contact one line 16 which goesto the high: beam'light relayon thecaryandin itsother position engages a contact 1! on a line 78 which goes to the low beam light relay on the car.

The phototube P is an electron-multiplier phototube. It includes an illuminated cathode I9 which is connected by a line 89 to the line 35, and which line includes a resistor SI. This resistor 8i is a voltage compensation resistor. The phototube P also includes a plurality of reflecting electrodes or dynodes 82, 83, 84, 95, 89, 81, 88, 89 and 99. The anode 9| of the phototube P is connected to the shielded line 99. Extending from the line 99 to a grounded connection indicated at 92 is a line 93. Connected to this line 93 is a line 94 that goes to the dynode 82. Also connected to the line 93 is another line 95 which goes to the dynode 83. Likewise another line 99 extends from the line 93 to the dynode 84. Still another line 91 extends from the line 93 to the dynode 85. Another line 98 connects the line 93 to the dynode 88. dynode 81. Another line I90 connects the dynode 89 to the line 93. Another line IIlI connects the dynode 89 to the line 93, and a line I92 connects the dynode 99 to the line 93.

Included in the line 93 are a plurality of neon lamps. These neon lamps are watt lamps without any resistors in the bases. A pair of the neon lamps are included in the line 93 between the connections of the lines 89 and 94 thereto. These are designated 93. A second pair of neon lamps I99 are included in the line 93 between the connections of the lines 94 and 95 thereto. A third pair of neon lamps I95 are included in the line 93 between the connections or the lines 95 and 99 thereto. A neon lamp I99 is included in the connections between the lines 99 and 97. Another neon lamp I98 is included in the connections between the lines 91 and 98. Still another neon lamp 199 is included in line 93 between the connections of the lines 98 and 99. Another neon lamp H9 is included between the lines 99 and I99. Still another neon lamp III is included between the lines I99 and I91, and another neon lamp H2 between the lines I9! and I92. Two more neon lamps H3 and H4 are included in the line 93 between the connection of the line I92 thereto and the grounded connection 92.

A condenser H5 of 100 n. is connected in parallel across the pair of lamps I95 between the lines 95 and 96. Another condenser IIS of 200 loaf. capacitance is connected in parallel across the lamp I99 between the lines 97 and 98. Still another condenser II! is connected in parallel across the lamp I99 between the lines 98 and 99. This condenser Iil has a capacitance of 300 ,u f. Another condenser I 28 is connected in parallel across the lamp H9 between the lines 99 and 299 and has a capacitance of 400 ,lL/Jf. Another condenser I I9 is connected in parallel across the lamp III between the lines :99 and IN and has a capacitance of 600 ,c tf. Another condenser :29 is connected in parallel across the lamp II2 between the lines ml and I92 and has a capacitance of 1000 ,upf. Still another condenser I2I is connected in parallel across the lamp H3 and has a capacitance of 1500 t, while still another condenser i22 is connected in parallel across the lamp H4 and has a capacitance of 2000 t.

The voltage drop across each neon lamp remains very nearly constant regardless of the amount of current through that lamp. Thus, the voltage across the string of lamps remains constant regardless of normal variations in volt- Another line 99 connects the line 93 to the age or" the cars battery. This makes the unit entirely automatic and there is no necessity for any variable control which the driver must change to compensate for changes in battery voltage, the change of load on the battery, or the generator charging rate. through I22, inclusive, which are connected across the neon lamps, cause the lamps to light consecutively rather than all at the same time. This helps to smooth out the voltage peaks on each half of the cycle and maintains a more nearly constant output from the phototube.

Operation While the manner in which the automatic headlight control above described operates is believed to be obvious from the description of parts given, it may be briefly outlined as follows.

When the driver of a car in which one of these controls has been installed is desirous of rendering the control effective, he closes the switch 3!. Assuming that there are no oncoming cars within effective range, the plates 4! of the relay R will hold the switch plate 73 in engagement with the contact 15 and thereby complete the circuit to the high beam light relay through lines 2|, l4 and 76.

The phototube P is excited by the secondary coil 32 and the various connections thereto, which include the bank of neon lamps and the condensers which are connected thereacross. The secondary 39 also produces a voltage which passes through the lines 49 and 51, resistor 52, line 54, and resistor 53 to the grounded connection This voltage from the secondary 39 will not pass through the relay coil 49 because under normal conditions it cannot cross the thyratron tube V, the latter being in such condition that the electric current will not pass from the anode 46 to the cathode 55.

However, when the light from an approaching vehicle strikes the phototube P, the grid of the thyratron tube is affected to cause the tubeto fire. This means, of course, that the current flows thereacross and as the current now crosses the thyratron tube, it will also pass through the relay coil 49. This affects the plates M to draw the switch plate I3 away from the contact 75 and into engagement with the contact 11, thus breaking the circuit to the high beam light relay and completing the circuit to the low beam light relay.

Just so long as there is sufficient light on the phototube P to maintain the grid of the thyratron tube excited, current will pass therethrough and also through the relay coil, thus holding the switch IS in position for compl ting the circuit to the low beam light relay. However, after the oncoming vehicle passes the car having the control, there is no light which strikes the phototube P. The grid of the thyratron goes cold and the circuit therethrough, of course, is interrupted. This also interrupts the circuit through the relay coil 49 and thus the circuit to the low beam light relay is broken, while the circuit to the high beam light relay is restored.

While preferred specific embodiments of the invention are hereinbefore set forth, it is to be clearly understood that the invention is not to be limited to the exact mechanisms, devices, and circuits illustrated and described, because various modifications of these details may be provided in putting the invention into practice within the purview of the appended claims.

What is claimed is:

1. In an automatic headlight control, a photo- The condensers I I 5 l tube adapted to be mounted in position on a car in which said control is installed wherein it receives light from the headlights of an approaching vehicle, said phototube including an illuminated cathode, an anode, and a plurality of dynodes, a vibrator adapted to be connected to the battery of said car to convert the direct current from said battery into alternating current, a power transformer including a primary connected to said vibrator and a pair of secondaries, one of said secondaries being connected to the cathode and dynodes of said phototube, a relay connected to the other of said secondaries, a thyratron control tube connected in series with said relay and having a grid connected to the anode of said phototube, a switch included as a part of said relay and adapted to complete the circuit to either the high beam light relay or the low beam light relay in the car in which said control is installed, a grounded connection connected to said last mentioned secondary and bypassing said relay and thyratron control tube, and a resistor in said last mentioned connection.

, 2. In an automatic headlight control, a phototube adapted to be mounted in position on a car in which said control is installed wherein it receives light from the headlights of an approaching vehicle, said phototube including an illuminated cathode, an anode, and a plurality of dynodes, a vibrator adapted to be connected to the battery of said car to convert the direct current from said battery into alternating current, a power transformer including a primary connected to said vibrator and a pair of secondaries, one of said secondaries being connected to the cathode and dynodes of said phototube, a relay connected to the other of said secondaries, a thyratron control tube connected in series with said relay and having a grid connected to the anode of said phototube, a switch included as a part of said relay and adapted to complete the circuit to either the high beam light relay or the low beam light relay in the car in which said control is installed, a line extending from a grounded connection to said last mentioned secondary and by-passing said relay and thyratron control tube, a fixed resistor in said line, and a variable resistor in said line connected to the cathode of said thyratron control tube.

3. In an automatic headlight control, a vibrator, a power transformer including a primary connected to said vibrator and a pair of secondaries, one of said secondaries being a high voltage secondary and the other a low voltage secondary, a phototube including an illuminated cathode, a plurality of dynodes, and an anode, a

connection between said high voltage secondary and said cathode, a grounded line connected to said connections and including a series of neon lamps, connections between said grounded line and said dynodes, condensers of different capacities connected across certain of said neon lamps, a relay connected to said low voltage secondary, a thyratron control tube connected in series with said relay and having a grid, and a connection between said grid and the anode of said phototube.

4. In an automatic headlight control, a vibrator, a power transformer including a primary connected to said vibrator and a pair of secondaries, one of said secondaries being a high voltage secondary and the other a low voltage secondary, a grounded line connected to said primary including a variable resistor and a manually operable control switch, a phototube including an illuminated cathode, a plurality of dynodes, and an anode, a connection between said high voltage secondary and said cathode, a grounded line connected to said connections and including a series of neon lamps, connections between said grounded line and said dynodes, condensers of different capacities connected across certain of said neon lamps, a relay connected to said low voltage secondary, a thyratron control tube connected in series with said'relay and having a grid, a connection between said grid and the anode of said phototube, a low pass filter in said connection, a grounded line connected to said low voltage secondary and bypassing said relay and thyratron control tube, said last mentioned grounded line including a variable resistor connected to the cathode of said thyratron control tube.

ELBERT MATTHEW PARDUE. RALPH ORON HIGGINS.

REFERENCES CITED The following references are of record in the file of this patent:

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